The invention relates to data recording, and more particularly to control of recording power when recording information to alternating land/groove tracks on an optical disc.
In conventional phase-change optical discs, data is typically recorded on groove tracks. When data is recorded on groove tracks, land tracks guide laser beams and reduce crosstalk from adjacent groove tracks.
If data is recorded on both groove tracks and land tracks, density of data tracks may be doubled provided that the widths of the groove and land tracks are unchanged. Crosstalk between adjacent land and groove tracks may be reduced if the height differences between the land and groove tracks is ⅙λ (wavelength of light source). Therefore, using both groove and land tracks is feasible to attain higher recording density. Accordingly, optical discs utilizing land/groove configuration. such as DVD-RAM (digital versatile disc-random access memory) are developed, as well as opto-magnetic recording media such as ASMO (Advanced Storage Magneto-Optical) discs.
FIG. 1 illustrates configuration of a conventional optical disc comprising alternating land and groove tracks. As illustrated, the optical disk 10 is of a single-spiral configuration, in which groove track 11 and land track 13 are switched at header 151, and groove track 11 and land track 13 alternate along a single continuous spiral track. Each of the tracks is divided into a plurality of sectors 153 by the header 151 at the switch point and header 152 elsewhere in each revolution. In the illustrated example, there are 8 sectors per revolution, while in an actual design of an optical disc, there may be tens of sectors per revolution, and the number of sectors increases in the outer annular area.
FIG. 2 is a cross section of the described optical discs. Optical disc 20 comprises a plurality of alternating land tracks 22 and groove tracks 24. According to a conventional land/groove recording method, the same power level is used for recording data on the land and groove tracks, assuming that recording condition is the same for the land and groove tracks. Owing to the structural differences, however, the land and groove tracks have different recording conditions. Therefore, when recording on the land and groove tracks, a light beam of the same power may generate recording marks of different lengths on the land and groove tracks, respectively. As a result, bit error rate on groove and/or land track may increase. When recording information on both the land and groove tracks, recording power changes when recording track switches from a land track to a groove track, and vise versa.
According to a conventional method, when recording, intensity of light beams differs on land tracks and groove tracks. Type of data track is determined using information recorded on header field accompanied with each sector. For, example, physical ID (PID) within the header field may be used to determine whether the data track is a land or groove track. Additionally, the data track type may be determined using signals obtained from a preamplifier. These conventional methods, however, are error-prone, especially under situations of high noise or high rotation speed.
The present invention uses a predict mechanism to determine land/groove track switch, and determine a write power accordingly. According to the predict mechanism, a counter mode is initiated after one or more physical identification number(s) (PID) is (are) retrieved. In the counter mode, a land/groove switch point may be predicted, and write power is changed at the predicted land/groove switch point. According to a conventional method, when the PID is not obtained from the header information, the land/groove track switch point cannot be determined for lack of sector type information provided by the PID. The present invention, however, can correctly predict the land/groove track switch point even though the PID is not available for some time.
The invention relates to methods and systems for recording information on an optically readable storage media (referred to as “optical disc” hereinafter), predict the position of land/groove alternation of a disc formatted to accommodate advanced high-density information storage techniques, such as DVD-RAM.
Systems for recording and controlling recording on optical discs are provided. In an embodiment, a system for controlling recording on an optical disc is provided, wherein the optical disc comprises alternating land and groove tracks, each of which comprises a plurality of sectors identified by physical ID (PID). The system comprises a first counter, second counter, Land/Groove switch predict machine, processor, and a power controller. The first counter performs a bit count according to provided channel bit clock signals. The second counter performs a sector count responsive to the bit count obtained by the first counter. The Land/Groove switch predicts machine uses the result of bit count and sector count to predict the land/groove switch point. The processor uses the physical ID (PID) to determine the track type of a sector at which a recording operation initiates. The power controller determines a recording power for the recording operation according to the Land/Groove switch predict machine.
Also disclosed are systems for recording information on optical discs. The system records information on an optical disc having a track with alternate formation of a plurality of land and groove tracks therein, wherein each of the tracks comprises a plurality of sectors identified by physical ID (PID) thereof. The system comprises an optical head, a detector, and a controller. The optical head provides light to the optical disc, receives reflected light from the optical disc, and provides signals according to the reflected light. The detector decodes the physical ID (PID) from the signals provided by the optical head. The controller performs a bit count according to provided channel bit clock signals, performs a sector count in response to the bit count, determines the track type of a sector at which the recording operation initiates according to the physical ID (PID), uses the bit count to determine whether the recording operation proceeds to a following sector, and determines the position of the sector relative to a preset switch point where the land and groove track alternate according to the sector count, and predict the land/groove switch point using the result of sector count.
Also disclosed are methods of recording information. In an embodiment of such a method, an optical disc is provided, wherein the optical disc comprises alternating land and groove tracks arranged according to a preset configuration, and each track comprises a plurality of sectors Physical ID (PID) is provided, specifying a serial number of a sector to which data is recorded. The track type of the sector is determined according to the physical ID (PID) and the preset configuration. A counter mode is initiated after one or more physical identification number (s) (PID) is (are) retrieved. In the counter mode, a land/groove switch point may be predicted, and write power is changed at the predicted land/groove switch point.